This post was published long before the Mists of Pandara Expansion.
The tips and techniques explained here may be outdated.

Mage vs Warlock

On Twitter, Adam Holisky (a writer for Wow.com) wondered: Why do Warlocks hate Mages, and Mages hate Warlocks? You’d think they’d want to have each others babies.
Mages and Warlocks hate each other because:
– They keep stealing my clothes(necklaces, rings, trinkets, etc).
– Sibling rivalry, we both want to top the damage meters.
– We get smexy demons. Succubus or Felguard take your pick. They got.. um.. watery bubble thingy.
– We get cookies, they got biscuits. Cookies are cooler than biscuits.
– Because noobs keep asking me for a portal to Dalaran.
– Because shadow bolts are way sexier than frost bolts. Just sayin’
– Flame-y demon pony of WTFPWNage!!
– Lore wise, some warlocks are mages who have turned to demons/shadow-y arts. Some mages still resent us for it..
– They’re goody-two-shoes and a “hint of evil” offends them.

I think of warlocks as less retareded hunters, with a dash of frostfail and DoTs. Also with more retarded itemiseation (spirit?!), and pets. Pets are boring & annoying.
That’s why I play a Mage. Food, Portals, and absolutly NO PETS. (because the peeps who play frost are below warlocks on the respect-o-metre)